Shephard-generator - what is that ?

[Arnim X. Sauerbier]

>>The barbers pole is a great alusion to the audiable effect, 
>
>At the last CCRMA concert (a couple weeks ago), a David Jaffe piece
>was performed on Disklavier (Yamaha MIDI controlled grand piano).  It
>featured the baber's effect on piano!  He had a little motif/scale
>which ran down in pitch, and was done simultaneously in several
>octaves.  The bottom octave would fade out as the top octave was
>fading in, and it had just this effect.  It was *damn* cool to hear on

There's a CSOUND orchestra (patch) that does this. I don't recall the 
name.  (Sorry, it's been 5 years since I saw it, but the effect was* 
cool.)

Basically, you have a sequence of signals (sinewaves) at successive 
octaves.  The intensity of those signals is adjusted to fit a bell-curve 
(plotted with freq. in X, and intensity in Y).  Signals around the 
mid-range (ca 400 hz) are at the peak, decreasing as you go up or down.

The frequency of ALL those harmonics is slowly shifted upwards, in 
discrete semitones or continuously.  As the formant's frequencies shift, 
their intensity is adjusted to match that fixed bell curve.  I.e. high 
frequencies decrease in volume, low frequencies increase.  This continues 
until you have shifted all frequencies by an octave.

At that point, you have exactly the same set of frequencies/amplitudes as 
you did before.  You can loop the generated sound to get the continuously 
rising effect.

Csound is cool - but you wait 5sec to 5hours to hear results of your 
work, whereas tweaking a synth is immediate. 
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Arnim Sauerbier